Generating odontograph



Aug. 29, 1933. J. w. HUGHES GENERATING ODONTOGRAPH Filed Sept. 18, 1930 2 Sheets-Sheet 1 INVENTOR c/A/VIE8 W HUGHECS. BY

7 ATTORNEY Aug. 29, 1933. w HUGHES 1,924,405

GENERATING ODONTOGRAPH Filed Sept. 18, 1950 2 Sheets-Sheet 2 INVENTOR Big/M455 W HUG/15$.

% i ATTORNEY '7- -,7 of Fig. 6w.- .7 M i Fig. 8 is a diagrammatic illustration showing Patented Aug; 29, v1933 ;;.j. 9% 9 gomgmaa'rmo ODONTQGRAPH ration of Delaware Applicants swam-am, 1930'.

sem nar ans;

- 12 Claims. (01. sat-21 This invention relates to an instrument forgenerating an involute curve and describing the same on a drawing.

The main objects of the invention are ;.to' pro-.

vide' a; portable instrument ofthis; kind which may be, Operated upon a paper sheet or' Bristol board having'adrawing thereonso-as to allow the curve to be applied directlyto thedrawing; and to provide a deviceof this type which'is adapted to be selectively positioned ,so as to apply the curve at a predeterminedlocation onthe drawing. V v I Further objects of the invention areto provide a generating ,odontograph which is particu- '1 larly adapted for developing the curvature of an involute gear tooth on the layout'of the gear; to provide an instrument of this kind which may be adjustablyconditioned for layingoutthe involute'gear teeth of gears of various diameters;j

to provide aninvolute. curve generating device,

by which a previouslydevelopedinvolute curve may be conveniently checked; to providemeansl in a device of this for conveniently-locating the curve describing element 11113 predetermined position with respect to a base circle ot a gear layout; and to provide anodontographbywhich the reverse curvatures of the respectively opposite;

sides of involute gear teeth may be conveniently outlined- An illustrative embodiment of my invention is shown in the accompanying drawings; in which: 2 a :1 a 1* T Fig. 1 is a pl'an view of an;odontograph"illustrating the operation 'thereofrby which an inslideor bar 8 is shiftably mountedi is substantially longer thanthe head 2 of the] volute curve; is =Iormed. Fig 2'is a longitudinal onthe line 2-- 2 "of Fig. 1. '1

Fig; 3 is a transverse;yerticalrsection takeni on the line 3-3 of-Fig. 1, s Fig. 4 is a transverse section 4+4 of Fig. I; i v a v Fig. 5 is an enlarged vertical section takenon the line 5- 5 of Fig. 2. I Fig, 6 i s a;top plan view-of anodontograph' embodying a modified form ofymy invention;

"Fig. 7 is a verticaltion taken on theqline a conventional development of an involute curve. Heretoford'indayingout; involuteeear teeth, it has beencustomary to develop thednvolute curves by one" of the well geometric,- man-t od's; such a'sfthatshown in '8..

r this im "r i m wpis -FWjd? tances' to laid an on tangential construction 7 vert cal section taken on the line.

- end era the instrument;

lines; 5 Accurate measurements of this; type are difficult to obtain-and therefore itis the practice- -to;use ajcord of the; are. as a unit of measurement;

This procedure results in the formation of curves whicharej only approximately accurate and irequently giv'es rise to sufiicienterrorto cause 'ex cessive interference between the teeth :of; the gearsmade'in accordance with the drawing In curate. 7

of -anyi point on atang'ent to a 'curvethat rolls without sliding around ithe curve.

curve? In practicmthe'base circle of the gear is 'usedas the generating curveupon which a tanv gent is; in efiect; rotated without sliding; g

In the form. shown, the improved inyolutegenerating instrument includes, a T-shaped rotatable;

member having an extensible radiusarm 1 and a head 2 which is perpendicular to the length of;

the radius armn The radius arm is formed of a;

order to check-a curve that hasbeen developed geometrically, a similar process isfollowedat the *expense of considerable *timeand without a com; plete satisfaction that the final work isacpair of relatively slidable sections 3 and; 4 that:

are fixed 'in a selected relationby a thumbscre w 5 which is threaded in the section 3 and which.

bears upon a pressure plate 6. The pressure plate r 6 is carriedbythe section 3 andiitfrictionallyengages the upper surface of the extensible sec- 'tion 4,vas shown-in Fig; 2.

.Forme d'in the lower side of the head2'zof the instrument is a dovetailed groove '7 -in which a The bar 8 instrumentand it is providedfat its left end;as

arm lhas aasharp pointed pivot 11 on its outer spring 10. The extensible section 4 of the radius extremity which forms an axis about which the instrument is swingable The lower side of the slide"8 extends in advance 4 of the corresponding side of-the head 2 forming a suppo Journaled in bearings l2 ,,loca t ed' at the Juno- 1, tion of the radius arm 1 and the head- 2 ,isna

ro1ler 13 which extends-through registering slots 14 and 15 in the slideBand head 2, respedtively.

The-periphery of the roller 13bears upon 9. flex-.

ibletape lfi-which isrsecured'to the'lower surface- Q e s a d-w c ha e o d ed p tions-in registration withthegroove 174., The" tior the 4 wardly as shown at 17 in Fig. 5.

roller 13 extends downwardly beyond the normal plane of the flexible tape 16 and bulges the portion of the tape with which it contacts downthe curvature of the'arc. The thumb screw 5 is then released so as to permit the radius arm 1 to be extended until the crown of the roller 13 registers with the circumference of the are.

This seating of the radius arm may be conven iently accomplished by providing a concentric arc 21 on the drawing which has a radius that is shorter in lengththan the radius 'of the base v circle, an amount equal to the known distance between the bevel edge 19 of the instrument and a the crown of the roller. After-the bevel edge 19 has been placedin alinement with the are 21, the thumb screw 5 is tightened to fix the length of the radius arm 1.

The slide 8 is then shifted relative to the head 2 until the marker 9 coincides with the point pressing the central portions of the head 2 firmly from which the involute curve is intended to be drawn. Then the instrument is rotated in a clockwise direction, as viewed in Fig. 1, while upon the surface of the-paper upon-'which'the curveis being formed. 'The pressure upon the head of the instrument firmly holds that area of the flexible tape 16 which the roller IS bulges downwardly, in frictional engagement with the surface of the paper so as to prevent 'the'slide 8 from sliping or sliding relative to the locus" of the roller during rotation of the instrument. The roller 13 rolls upon the tape during rotation of the instrument and successively bulgesthe adjacent I portions of the tape outwardly, in the manner .shown in Fig. 5, thereby causing the slide to, in effect, roll 'withoutsliding upon'the circumference of the base circle. During this'movement' of the instrument, the left end portion of the slide 8 is projected outwardly from the'head 2fas illustrated in 'dottedlines at 22 in Fig. l and the marker 9 describes the involute curve illustrated at 23. Inorder to check the curve, the instruy A i ment is rotated from its dotted line position, shownat 24 in Fig.1, to its initial position and if the marker follows the same path during the return stroke of the instrument, it is substantially certain that the curve'described is a true involute.

.In the form shown in Figs. Sand 7, an odonto-' graph is illustrated having a marker at the respectively opposite'ends of the slide so as to enable' the describing of involute curves of reverse curvatures with a single instrument. I

The instrument shown in Fig. 7 includes-an extensible radius arm 1' and a perpendicularly transverse head 2' which are of'the'same general construction as the corresponding parts of the device shown in Fig. 1,- with the exception that" the head 2 is provided on its lower side with a dovetailed groove25 in which the dovetailed tongue 26 of a slide 8 isshiftably" mounted.

This slide'is provided with slots 2'7 and 28in its respectively opposite ends in which markers 29 and 30 of the form shown in Fig. 3 are located. The head' 2 is provided 'at its central portions A slot 18 formed with a roller 13 which is supported on a shaft that is journaled inbearings 12. The roller l3is located in advance of the outer edge 310i the head portion 2 and its periphery bears against a flexible tape 16 which is secured to the lower side of the slide 8' and whichextends outwardly beyondthe edge 31 of the headportion. The roller 13 normally bulges the portion of the flexibl'e tape with which it contacts downwardly, as

viewed in Fig. 7, forming a bearing point between the lower side of the tape and the surface of the "drawing paper upon which the instrument is placed during operation, at which sufficient friction exists to hold the slide against slipping or sliding. relative to the path in which the roller travels during oscillation of the instrument about its pivot 11'; r The radius arm 1 is provided with a slot 18 which has'a beveled edge 19' located at a known distance from the crown of the periphery of the roller so as to enable accurate placement of the instrument withrespect tothe base circle of a gear layout in the manner described above. 1

In the operation of this form of 'my invention,

one of the markers is preferably rendered inoperative by'placing a wedge or other suitable means under the spring thereof so as to hold the marker I out of engagement with the paper. When it is desiredtoform the curvature-of the right side of a tooth, the left marker 29 is rendered inoperative in this way and the instrument is rotated in a clockwise direction, as viewed in Fig. 6. To check the curve thus described, the instrument is then returned to its starting position so as to determine whether the marker follows the same course during both directions of rotation. The curvature of the left side of the tooth may be formed in the manner described in connection with Fig. 1 while holding the marker 30 of the right end of the slide out of contact with the paper.

With either of these forms of my invention, an-

involute curve may be'quicklyfa'nd accurately generated at any desired location ona gear layout or other drawing and previously" developed involute curves may be readily checked. Cone siderable time is saved by obviating the necessity of repeatedly constructing an involute curve on a drawing byone .of-the' conventional geometric methods, such as illustrated in Fig. 8 invwhich a plurality of radii 32 which subtend equ'al'arcs 33 are first constructedandthen tangents 34 to these arcs are drawn at the intersections 35 of the arcs and the radii. ,On'each tangent,- the accurate distance from a given point 36 on the circle, to" the intersection is stepped oh so as to,-in-effect, trace the end of aistraightedge as it;is-rolled upona circle.

Although but two specific embodiments of this" V The inaccuracies encountered in me asur-- ing the arcuate distances introduce substantial invention have herein'been'shown and described,

it will be understood that variousch anges in the size,-'shape and arrangement ofpartsmaybe made without. departing-from the spirit of my invention and it is not my intention to limit its scope other than by the terms of the appended claims. What Iclaim is! V 7 H a r s 1. Aninstrument fordeveloping an involute curve upon a plane surface includingarotatable her having a substantially flexible face engageable with said surface, and means for compressing suc member, a transverse slide mounted on said memlocus of a point on said thereof. 7

3.'An instrument for developing an involute,

surface so as to prevent slipping of said slide in a course tangent to the locus'of a point on said member during rotation of the'latter.

2. An instrument for developing an involute curve on a. plane surface including a rotatable means for compressing successive limited, areas of said face against said surface so as toprevent slipping of said slide in a course tangent to the curve upon a plane surface including an oscillat able radius arm, a transverse slide shiftably mounted on said arm forming a support for one end portion thereof and having a substantially flexible portion, amarker on said slide, and means for compressing successive limited areas of the flexible portion of said slide against said surface so as to prevent slipping of said slide in a course tangent to the locus of a point onsaid arm dur ing rotation of the latter. I 4. An instrument for developing an involute curve upon a plane surface including an oscil-.

latable radius arm, a transverse slideshiftably mounted on said arm having asubstantially flexie ble face engageable with said plane surface for supporting one end portion of said instrument thereon, and a roller journaled on said arm having its periphery in rolling contact with said face and adapted to compress successive limited areas of the latter against said plane surface for hold-'- ing said slide against slipping in a course tangent to the are described by said roller during rotation areas of. said face against said surface so as to of said arm.

5. A generating odontograph including a rotatable radius arm, a transverse slide slidably mounted on said arm, a flexible tape on the lower side of said slide for supporting the latter on a plane surface and a roller journaled on said arm having its periphery in rolling contact with said tape 1" or pressing successive adjacent areas thereof against a plane surface so as to hold'said slide against slipping in a tangent course relative to the path of said roller during rotation of said arm.

6. A generating odontograph including a rotatable radius arm, a transverse. slide slidably,

mounted on said arm, a flexible tape on said slide, and a roller journaled on said arm and bearing outwardly on said tape, the periphery of said roller protruding beyond the normal plane of said tape so as to bulge the latter outwardly at a limited area.

7. In a generating odontograph, a rotatable radius arm, a pivot on one end of said radius arm, a slide shiftably mounted on the other end thereof having asubstantially flat flexible face for supporting one end of said odontograph on a plane surface, said arm having guiding elements thereon' for constraining the movement of said slide to a path perpendicular tothe longitudinal axisof said arm, and means for pressing successive limited areas of said flexible face upon said plane surface so as to hold said slide against slipping in a course tangent to the locus of a point on said arm during rotation of the latter.

arm during rotation t 3 8. In a generating odontograph, an extensible radius arm. including a pair of 'slidably connected sections, a pivot on one of said sections, aslide 1 mounted on the other section having a substan f tially flexible face for supporting one end of said odontograph on a plane surface, said slide being shiftable perpendicularly with respect to the longitudinal axis "of said arm, means for pressing.

successive limited areas of said slide against said plane surface for preventing slipping of said slide fixing the sections of said arm in a selected rela-I.

tion so as to predetermine the radiusof the locus of saidpoint.

side of said radius arm spaced from said head por tion, a bar slidably mounted on said head portion forming a support therefore during oscillation of 9. A generating odontograph including a .T- shaped oscillatable member having a radius arm and a perpendicular head portion, a pivot onone said member about said pivot, a marker on said bar, a flexible tape on the supporting side of said a bar having anexposed edge portion, and' a roller journaled on'saidT-shaped oscillating member engaging the exposed edge portion of said flexible tape for holding a limited area thereof in fricf of said roller.

10. An instrument for developing an involute curve on a substantially plane surface including tional engagement with a supporting surface so as i to prevent sliding of said bar relative to the path a a rotatable radius arm, a slide mounted on said arm, said slide having a flexible face receivable .on said plane surface said slide being shiftablei perpendicularly with respect to the length of said arm, a pair of markers, oneat each end of said slide, and means for pressing successive, limited 11. In a generating odontograph, an extensible radius a'rmi'ncluding a pair of slidably connected sections, a pivot on one of said sections, a slide mounted on the other section, said slide being shiftable perpendicularly with respect to the longitudinal axis of said arm, a flexible tapeon said slide, and a roller journaled on said arm and bear:

ing outwardly on said tape, the periphery of-said roller protruding beyond the normal plane of said tape so as'to bulge the latter outwardlyat a limited area.

12. In a generating odontograph, an extensible' radius arm including a pair of slidablyconnected' sections, a pivot onone of said sections, a slide mounted on the other section, said slide being a I shiftable perpendicularly with respect to the longitudinal'axis of said arm, a flexible tape on said i v slide, a roller journaled on said arm and bearing outwardly on said tape having a periphery pro truding beyond the normal plane of said tape for bulging the latteroutwardly at'limited areas so as to prevent slipping ofsaid slide in a course tangent to the locus of said roller during rotation of said arm, and means for fixing the sections of said arm in a selected relation so as, to predetermine the radiusof the locus of said roller.

JAMES iw, HUGHES. 

